The Great Hall at Cooper Union was an important meeting place in its time. In 1859, nearly 2,000 merchants packed the hall, under the auspices of the Democratic Merchants Association, led by August Belmont and William B. Astor. Their purpose was to oppose Republican anti-slavery efforts and to assure the South that New York merchants could be trusted.

Abraham Lincoln, a contender for the Republican nomination for the presidency, spoke there (2/27/1860) shortly after John Brown, the anti-slavery crusader, raided Harper's Ferry. Lincoln disavowed Brown and tried to strike a conciliatory tone with the South. He did oppose the expansion of slavery and stated:

'…You charge that we stir up insurrections among your slaves. We deny it; and what is your proof? Harper's Ferry! John Brown!! John Brown was no Republican; and you have failed to implicate a single Republican in his Harper's Ferry enterprise. If any member of our party is guilty in that matter, you know it or you do not know it. If you do know it, you are inexcusable for not designating the man and proving the fact. If you do not know it, you are inexcusable for asserting it, and especially for persisting in the assertion after you have tried and failed to make the proof. You need to be told that persisting in a charge which one does not know to be true, is simply malicious slander….'

'It is exceedingly desirable that all parts of this great Confederacy shall be at peace, and in harmony, one with another. Let us Republicans do our part to have it so. Even though much provoked, let us do nothing through passion and ill temper. Even though the southern people will not so much as listen to us, let us calmly consider their demands, and yield to them if, in our deliberate view of our duty, we possibly can…..'

'Wrong as we think slavery is, we can yet afford to let it alone where it is, because that much is due to the necessity arising from its actual presence in the nation; but can we, while our votes will prevent it, allow it to spread into the National Territories, and to overrun us here in these Free States? If our sense of duty forbids this, then let us stand by our duty, fearlessly and effectively. Let us be diverted by none of those sophistical contrivances wherewith we are so industriously plied and belabored — contrivances such as groping for some middle ground between the right and the wrong, vain as the search for a man who should be neither a living man nor a dead man — such as a policy of 'don't care' on a question about which all true men do care — such as Union appeals beseeching true Union men to yield to Disunionists, reversing the divine rule, and calling, not the sinners, but the righteous to repentance — such as invocations to Washington, imploring men to unsay what Washington said, and undo what Washington did.'

'Neither let us be slandered from our duty by false accusations against us, nor frightened from it by menaces of destruction to the Government nor of dungeons to ourselves. Let us have faith that right makes might, and that in that faith, let us to the end, dare to do our duty as we understand it.'

The Cooper Union Building was designed in 1859 by Frederick A. Peterson. Peter Cooper gave $1 million dollars to the school in his lifetime.

Lincoln ran successfully for president as a Republican in 1860. On his Inauguration Day, seven Southern states had seceded from the Union, and four more would follow. When the war started, he repressed civil liberties and rallied the nation. In 1863, he freed the slaves with his Emancipation Proclamation. Later that year, he gave the Gettysburg Address that memorialized fallen soldiers, of which there were many. He suppressed the New York City draft riots in 1863. Lincoln beat his former general George McClellan in the 1864 presidential race. Five days after Confederate General Robert E., Lee surrendered on April 19, 1965, Lincoln was assassinated by John Wilkes Booth while attending a play at Ford's Theater in Washington, DC. He died the next morning. On its way back to Illinois, Lincoln's body laid in state in downtown New York at City Hall. He is buried in Oak Ridge, Illinois, near Springfield.

For the B&O railroad, he invented a small brass steam engine —'Tom Thumb.' It replaced open horse-drawn cars, and hauled passengers at the record of 18 miles per hour. His invention sparked a railroad boom. Cooper made his first fortune selling steel rails to the B&O railroad. He went on to introduce the first structural beams for fire retardant buildings, and he introduced the Bessemer Steel process to the United States, with help from Andrew Carnegie. He helped finance the first transatlantic telegraph cable.

As a social reformer, he sought to professionalize the police and fire departments, improve prisons, and supply clean drinking water. He led a campaign against tenement houses. He founded Cooper Union, which had free tuition and a free reading room. He was unsuccessful in his bid for the presidency in 1876 as a Greenback. Cooper lived frugally in Gramercy Park, with only one servant. There were often long lines of men and women in front of his home waiting for donations. He is buried in Green-Wood Cemetery.